TCF is Time Correction Factor, which is multiplied times a boat's Elapsed Time
to give its Corrected Time.

To estimate relative progress, first calculate (conveniently, prior to the
race) a Speed Quotient (SQ) for each yacht you want to compare. SQx is equal
to the difference between your own TCFo and the TCFx of the other yacht (yacht
x), divided by the TCFx of yacht x. To estimate the time (in minutes) you get
from (or give to) yacht x at any point in the race, say at a mark, multiply the
SQx you calculated for yacht x times the number of minutes you have taken so
far in the race to get to that mark.

SQx = TCFo - TCFx = minutes of difference per minute
elapsed so far in the race
TCFx

*Rating (RAT) before adjustment for penalty (PE)